Factors influencing shell deposition during a tidal cycle in the intertidal bivalveCerastoderma edule

Abstract
The thin band between growth increments in the shell ofCerastoderma eduleis laid down at the end of the period of emersion, when the pH of the mantle and extrapallial fluids are at a minimum of pH 7·0 and 7·2 respectively. The growth increment is formed during immersion when the pH of the extrapallial fluid is 7·5–7·7 and the mantle 7·6–7·8, which is close to that of sea water (pH 7·8).